Three-time Olympic medalist Eliud Kipchoge became the first person to run a marathon in under two hours, clocking in at 1:59:40 as he passed the finish line Saturday morning in Vienna, Austria.

"It has taken 65 years for a human being to make history in sport, after Roger Bannister made history in 1954," Kipchoge, who's Kenyan, said in an interview with NTV Kenya shortly after the race.

Bannister broke the 4-minute mile record at an athletic meet in Oxford in May 1954.

"No human is limited," Kipchoge said.

Kipchoge, the reigning Olympic marathon champion, was already a leading figure in the race to break the 2-hour mark, which the race's organizer, chemicals company Ineos, called "the last great barrier of modern athletics."

Kenya's Eliud Kipchoge celebrates after busting the elusive two-hour barrier for the marathon Saturday in Vienna.

Alex Halada / AFP via Getty Images

The ability of a human to run that fast wasn't even considered possible until the 1990s. In 1991, Dr. Michael Joyner published a paper that estimated the fastest time for a human to run a marathon at 1:57:58.

"It's validating to me, but Mr. Kipchoge did all the running," Joyner said in a phone interview with NPR.

A short distance before the end of the 26.2 miles, a mere 20 seconds before the fabled two hours were up, Kipchoge pointed at the roaring crowds on either side of him, beating his chest as he crossed. He embraced his wife, Grace Sugutt, before his team piled in on a tidal wave of admiration.

Today we went to the Moon and came back to earth! I am at a loss for words for all the support I have received from all over the world.

"Today we went to the Moon and came back to earth! I am at a loss for words for all the support I have received from all over the world," Kipchoge tweeted.

A video posted on Twitter by the National Olympic Committee for Kenya showed the crowd in Eldoret, Kenya – Kipchoge's hometown – cheering and jumping as his record time was announced. According to Citizen Digital, a Kenyan news organization, Kipchoge will have a street named after him in Eldoret when he returns.

On the Hauptallee, a stretch of tree-bordered road that runs through Prater park, where the course was set, teammates lifted Kipchoge up on their shoulders, draping a Kenyan flag around his shoulders.

In several interviews, Kipchoge has compared his attempt to beat two hours to the effort that goes into putting a man on the moon.

Kenya's Eliud Kipchoge's sub-two-hour time, although unofficial, is another achievement in the world of marathon running for the Olympic gold medalist.

ALEX HALADA / AFP via Getty Images

Kipchoge, 34, had come to dominate the world of marathon running, winning the Chicago Marathon in 2014, the Berlin and London marathons in 2015, and the London Marathon in 2016.

He competed in the 2016 Summer Olympics in Rio de Janeiro, snagging the gold medal in the marathon.

The following year, 2017, saw Kipchoge win another Berlin Marathon and participate in Nike's Breaking2 event, a marathon held on a Formula One racetrack in Monza, Italy. It was the first marathon Kipchoge ran where he sought to break the two-hour mark, assisted by a team of pacesetters who acted as a windshield running in a V-formation around him. The assistance would mean that, if he beat two hours, the record would stand as unofficial.

On May 6, 2017, he crossed the finish line in Monza 25 seconds past the two-hour mark.

Undeterred, in 2018 Kipchoge won the London Marathon, then turned around and competed in the Berlin Marathon later that year.

At the time, the men's marathon world record was 2:02:57, held by fellow Kenyan marathoner Dennis Kimetto. Kipchoge beat that time by a minute and 18 seconds, coming in at 2:01:39. He now held the men's world record for the first time in his life.

If he had stopped then, he would have gone down as one of history's best marathoners. But the glory of the record in Berlin meant that legendary sub-2-hour record, which had eluded him a year before, was back in his sights.

Saturday's feat that tested the upper limits of physical prowess, however, will not be officially recognized as a world record by the International Association of Athletics Federations, much like the Breaking2 event. The race, held in Prater park in the heart of Vienna, was not an open event, the course in the park was evened ahead of time and Kipchoge had a team of 41 pacesetters with him, running in rotating teams of seven.

"Remember, the 41 pacemakers are among the best athletes ever, in the whole world," Kipchoge said. Among them was Matthew Centrowitz, who earned a gold medal for the U.S. in the men's 1500 meters at the 2016 Summer Olympics.

Kipchoge was also guided by an electric car that projected a green laser, moving at the pace needed to beat two hours, according to the IAAF.

Kipchoge's shoes were also the subject of much interest. He tied on Nike's new model of the NEXT% shoe, equipped with a carbon-fiber plate.

Dr. Joyner said it is all about maximizing the runner's energy economy.

"There's less energy loss with each foot strike. They've tuned it so that the recoil properties of the shoe optimize the ability of the runner to apply force to the ground."

Between the shoes, the pacers, the closed race and the electric car, Joyner said that the phrase "assisted" in conjunction with Saturday's marathon needs to be put in context, especially in comparison to Roger Bannister's mile 65 years ago.

"Bannister had two pacers, the track at Oxford had been recently refurbished, Bannister was a medical student working on maximum human performance, and his shoes had special ultralight spikes," Joyner said. "I see many parallels between him and Mr. Kipchoge."

"Hearty congratulations @EliudKipchoge. You've done it, you've made history and made Kenya proud while at it. Your win today, will inspire tens of future generations to dream big and to aspire for greatness. We celebrate you and wish you God's blessings." - President Kenyatta

The lack of sanction has, however, not deterred Kipchoge's supporters. He's now trending on Twitter, and many professional runners and other athletes have voiced their support, like four-time Tour de France winner Chris Froome. According to The Associated Press, Kenyan President Uhuru Kenyatta called Kipchoge shortly after the race.

"You've made history and made Kenya proud while at it," Kenyatta tweeted.